I've been noticing similar bugs in battery levels since I updated to 5.1.1. Just yesterday, I noticed the battery was showing 53%, but as soon as I plugged in, it changed to 14%
Run your battery all the way down to calibrate it, maybe.
Why after my phone is unplugged and battery drops to let's say 90-91% after restart of the device it raises up to 95-96%. What is wrong with the battery-meter?
Always happened to me with or without a jailbreak.Never experienced this before the jailbreak...